Three-dimensional ground displacements from static pipe bursting in stiff clay

Three-dimensional ground surface displacements from 20 m long static pipe-bursting experiments are reported. These experiments were conducted with firm-to-stiff clay backfill in a trench with very stiff clay sidewalls at three different burial depths. Multiple digital cameras and image analysis were used to quantify the surface response as the expander progressed through the original pipe. The experiments quantified the upward surface movement as the expander approached, the effect of burial depth on maximum uplift, and the final amount of uplift after it decreased to a residual displacement. The experiments also quantified the axially forward ground surface movement as the expander approached, reaching maximum just ahead of the expander, and decreasing to almost zero after the expander had passed by. Lateral movements of the ground surface away from the centreline are also reported, which were essentially zero at the centre line, increasing to a maximum and then decreasing with distance from the centreline. The three different burial depths produced in effect the same width of vertical surface response with the displacements contained within 1.5 m on either side of the centreline, suggesting that the very stiff clay trench walls had a dominant influence on the measured displacements.